The only place where you will see the email is in the url which opens the web browser when you create a new calendar in Rainlendar. After that Google will provide an authentication token that is used in all communication. If you have already given Rainlendar the permission to access your Google calendar (i.e. it already has the authentication code) then you won't see your email in any of the http queries.

The email address that you give when you create a new calendar is just a hint which the Google's website uses to pre-fill the sign in field. If you have already signed in to your Google account then the given email address is not needed for anything (or well, Google uses it to check if it's the same as the signed in user and if not, it gives a possibility to change the signed in account. At least it did in my case).

Well, after some weeks of use, I can tell the new Google Agenda v3 connection is not working.
The events I create with that calendar are not stored into Google Cal, and does not sync with my other apps.
The old version GoggleAgenda Obsolete is working well.
My events are stored instantly, and thus do sync with all my devices.